This invention relates to compounds containing a thio-ester group, and in particular to thio-ester compounds having liquid crystalline properties. The invention also relates to use of thio-ester compounds in liquid crystalline materials, and to use of thio-ester compounds, and materials containing thio-ester compounds, in devices.
Liquid crystal materials and their uses in electro-optical display devices are well known. The most commonly used types of liquid crystal materials are those which can utilise their nematic properties within such devices as the Twisted Nematic (TN) device, Supertwist Nematic (STN) device and Electrically Controlled Birefringence (ECB) device.
Thio-ester compounds are known, and are described in for example S. R. Pandas et al, Synthesis, (1983), pp 605-621: Z-C Chen et al, Synthesis, (1988), pp 723-724; and B. S. Pedersen et al, Bull Soc. Chim. Belg., (1978) Vol 87 pp 293-297. Liquid crystalline thio-ester compounds are described in M. E. Neubert et al Mol. Cryst. Liq. Cryst. (1981) Vol 76, pp 43-77. Thio-ester compounds are also described in German patents DE 2603293, DD 0145914, Japanese patents JP 550023129, JP 560108761, JP 600163858, Isr. J. Chem., 1980, volume data 1979, volume 18 (3-4), pages 197-198; J. Prakt. Chem., 1979, volume 321 (4), pages 619-628.
Liquid crystal materials are generally mixtures of compounds which individually or together show a liquid crystal phase. A number of desirable characteristics are sought in such compounds and materials. Among these are chemical stability, persistence of appropriate liquid crystal phases over a wide temperature range preferably including room temperature, and for some devices a high birefringence (.DELTA.n) is sought.